Pet door



FIG. 1 is a perspective view of a pet door showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a top view thereof;

FIG. 5 is a bottom view thereof;

FIG. 6 is a left side elevational view thereof; and,

FIG. 7 is a right elevational view thereof. 

The ornamental design for a pet door, as shown and described. 